Images are often generated on transparencies or slides so that they can be projected onto a screen. Typically a projected image is magnified substantially relative to its original size on the slide. In many cases, an image is formed on a slide with undesired artifacts or anomalies. When these anomalies are magnified in a projection of the image, they lend a displeasing character to the projected image.
These anomalies are produced by various phenomena during the generation of an image on a slide. For example, a photographic emulsion may display its crystalline configuration. This type of anomaly is referred to as "graininess". Another type of image anomaly occurs when slide images are produced by a thermal printing process.
In thermal printing, computer generated image data is supplied to a modulated laser. The laser is used to transfer dye from a dye-donor film to a surface of a slide on which an image is desired. In the context of thermal printing, the slide is typically referred to as a receiver.
In one particular form of thermal printing the receiver is a transparency or slide in 35 mm format (i.e., 1 inch by 1.5 inch). A thermal printer that produces such slides is disclosed in U.S. patent application Ser. No. 457,593 (S. Sarraf), entitled "Thermal Printer" and referred to in the Related Patent Applications section hereinabove.
When slides are produced by thermal printing, a dye-donor film is used that contains spacer beads in a dye coating. These types of dye coatings are disclosed in U.S. Pat. No. 4,772,582, issued Sep. 20, 1988. The spacer beads are very small, typically eight to fifteen microns in diameter. However, as a laser passes over a spacer bead, a "shadow" of the bead (i.e., a spot with low dye density) is formed in the image. These shadows, if left intact, produce visible anomalies in an image that is projected onto a screen from such a slide.
It is desirable therefore to produce such slides so that these visible image anomalies are not present in projected images.